Mordekaiser

Patch 7.2d raised Darkness Rise's magic penetration at rank 4 from 7% to 12% and cut Death's Grasp's cooldown at every rank. His win rate clears 50% in every bracket except Rift Apex, and from Diamond up he is banned more often than in the all-ranks pool. Realm of Death isolates a target one-on-one, steals 8% of their base stats, and lets him close out the fight.

Cho'Gath

He has had no direct patch changes, yet at the higher ranks he is banned in roughly one game in three, and his win rate still clears 50%. Each Feast stack adds 80-160 max HP and extends his attack range by up to 75. The more he finishes off, the tougher he gets and the further he reaches.

Garen

Patch 7.1e cut Perseverance's regeneration, and Judgment's armor shred fell from 15% to 10%. He still holds a high spot in the upper bands because his win rate stays steady around 50% and he is almost never banned. Decisive Strike's silence and Demacian Justice's true damage make a weakened target hard to let slip away.

Dr. Mundo

He has had no direct patch changes, and he is almost never banned. What holds his ranking up is his win rate in Diamond and Master. At Challenger it drops under 50%, and at Rift Apex it falls further still. Goes Where He Pleases cancels one immobilizing effect outright, and Infected Bonesaw takes 20-29% of a target's current HP, so it bites hardest against tanky opponents.

Sett

He has had no direct patch changes, and his ban rate stays low. What holds his ranking up is how often he is picked. His win rate sits right on 50% at Master and slips under it from Challenger up. Haymaker banks 100% of the damage he takes, up to half his max HP, and returns it as a shield plus true damage, so the more he is hit the more he gives back.

Darius

In 7.2, Crippling Strike began refunding half its cooldown and all its mana cost whenever it lands the killing blow. Clearing the wave and keeping Hemorrhage stacks no longer pull against each other, and his pick rate stays near the top of the role. His win rate sits right on 50%, tipping either side depending on the bracket. He places well in the jungle too.